Caterpillar ECU repair, need N548AB replacement?

[CapLeaker]

The topic is quite old but I would like to add some details for information.

I came across a fan control unit with the same transistor. It has a part number of 75344G and it looks like it is a N-Channel MOSFET HUF75344G3 (75A, 55V).

That’s awesome!

[Stepa]

The topic is quite old but I would like to add some details for information.

I came across a fan control unit with the same transistor. It has a part number of 75344G and it looks like it is a N-Channel MOSFET HUF75344G3 (75A, 55V).

[sam_sam_sam]

Re: Catapillar ECU repair, need N548AB replacement?

Oh well... at least I still have a job.

I guess that that you still have a job and they have not closed down because of the corona 19 virus

I been there which was not fun

[CapLeaker]

Re: Catapillar ECU repair, need N548AB replacement?

a very large percentage in my fix later pile does get fixed at some point. Actually during the shutdown I had all the time I needed to reduce my fix later pile down to zero. Currently this ECU is my only thing in the fix later box! I guess I did pretty good. My problem at the moment is, that I have way too many things going that need to be done before it gets too cold outside. Work is total nuts these days and everybody wants something done or fixed before it's getting cold outside. Oh well... at least I still have a job.

[sam_sam_sam]

Re: Catapillar ECU repair, need N548AB replacement?

My fix later pile is the same way but some of the time it does get fix but far more of them become parts

[eccerr0r]

Re: Catapillar ECU repair, need N548AB replacement?

My "fix later pile" tends to end up being the spare parts pile

[CapLeaker]

Re: Catapillar ECU repair, need N548AB replacement?

Well, I guess that thing goes in my “fix later pile”… for some crappy winter day or another boring lockdown. Thanks anyway guys for all the ideas!

[eccerr0r]

Re: Catapillar ECU repair, need N548AB replacement?

Just saying, it's just as easy to make fakes and even cheap chinese knockoffs would work as good or even better than the original at much lower cost!

[stj]

Re: Catapillar ECU repair, need N548AB replacement?

not fakes, i mean "recycled" / "re-directed" from the official production.

it happens a lot,
smd stuff is on reels of 500-5000,
they dont wait for the reels to run out before swapping them - where do you think the short reels of a few dozen to a few hundred parts go? in the trash? LOL
there is a shopping plaza in shenzen 10 floors high - nothing but component sellers.
i'm sure it's not a coincidence that it's in the same region as all the production companies!

[eccerr0r]

Re: Catapillar ECU repair, need N548AB replacement?

You know, they probably did sell "surplus" TO247SHT's... easiest device to make fakes of...

but then people noticed they were dead from the get go and refunded all of them...

Wasn't worth it.

[sam_sam_sam]

Re: Catapillar ECU repair, need N548AB replacement?

This might be reason that you could not find any information about the part number if it is that it is just a jumper

And

STJ

Might be right that they want you to think that it is not repairable

[stj]

Re: Catapillar ECU repair, need N548AB replacement?

it's probably to make it seem unrepairable.
now wouldnt it be funny if you found them in aliexpress - "surplus" from the manufacturing plant!!

[Agent24]

Re: Catapillar ECU repair, need N548AB replacement?

Look at my first post. It is clearly a fairchild device. It's heat sinked to the casing, not to the board.

Oh I must have missed that.
It could possibly be designed to draw heat up the pins and dissipate out through the back plate?

I've seen mini heatsinks on a slot A motherboard that were soldered to the board.

[eccerr0r]

Re: Catapillar ECU repair, need N548AB replacement?

usually, mechanical/assembly reasons

You do realize there are 0 ohm resistors out there, full ceramic resistors that have a single black line on it... why use it when a bare wire works...

Just that when they have multiple SKUs using the same PCB it's easier to replace different parts than retooling the pick and place with jumpers.

[CapLeaker]

Re: Catapillar ECU repair, need N548AB replacement?

Why make such a device for a dummy short. Much cheaper to put a piece of wire in!

[eccerr0r]

Re: Catapillar ECU repair, need N548AB replacement?

Something definitely went sour inside on pin 3 and blew through that plastic and shorted out to the heat sink part on pin 2.

Or as I postulated early on, it was welded that way to begin with!

If it was a diebond that shorted through a die... it sure would not have separated like that, diebonds are physically weak and the die soldered to the metal would hold on, and you will get the die remnants.

So yes, you got SHorT dummy device here and need to look elsewhere for issues, perhaps that other device that connects to these dummies -- is that shorted?

[CapLeaker]

Re: Catapillar ECU repair, need N548AB replacement?

but you have no silicon wafer - there is no semiconductor on the heatsink - never was!!

Sadly I have to agree here.

[CapLeaker]

Re: Catapillar ECU repair, need N548AB replacement?

How thick is the metal portion in the "heatsink" portion?

Not familiar with TO247AC construction since it was meant to be isolating, but a TO220 and TO3P the die is bonded straight to the heatsink pad which is really thick compared to the pin... so it can conduct heat away from the die.

What I'm seeing is that the heatsink pad is ... really thin? Thin enough so that it can actually be torn?

Die should be soldered to the heatsink pad, decapsulation usually damages die bonds. Also centered to reduce thermal resistance...

As much damage as it's taken now, is D-S still shorted?

The heat sink part is thick and really heavy compared to the top part. I am talking 1.6 gram vs 4.0 grams.O.k. put it this way: the short was between the middle pin 2 and the last pin 3. Something definitely went sour inside on pin 3 and blew through that plastic and shorted out to the heat sink part on pin 2.

It would be interesting to find out what is this device because things are not adding up to exactly what this device is

No kidding... that's why I put it here. A mystery device and a weird circuit. Couldn't pass that.

Maybe I'll put that top part on my belt sander and see what that does.

[eccerr0r]

Re: Catapillar ECU repair, need N548AB replacement?

oh wait, well at least I'm not the only one who hasn't fully awakened yet... of course it's not going to conduct

The photos are convincing to me now, SHorT.

[sam_sam_sam]

Re: Catapillar ECU repair, need N548AB replacement?

It would be interesting to find out what is this device because things are not adding up to exactly what this device is